1. Field of the Invention
The present invention relates to an optical axis adjusting device for automotive lamps such as a headlight, fog lamp or the like, and more particularly to an optical axis adjusting device provided in an automotive headlight having a movable lamp unit, to adjust the headlight optical axis with the lamp unit tilted vertically and horizontally with respect to a car body by turning an optical-axis adjusting screw.
2. Related Art Statement
One of the prior-art optical axis adjusting devices for automotive headlights is known from the disclosure in the U.S. Pat. No. 5,083,244, for example. It will be described herebelow with reference to FIG. 1. As shown, the automotive headlight includes a lamp unit 100 comprising a lamp housing 101 and lens 102 which define together a bulb space (not shown) in which a lamp bulb (not shown) is provided. When turned on, the lamp bulb emits a light beam which is projected forward in a predetermined luminous distribution pattern through the lens 102. The lamp unit 100 is mounted to a car body 103 by means of a pivot mechanism 104 tiltably in the horizontal and vertical directions. The optical axis adjusting device consists of a pair of optical axis adjusters each composed of an adjusting screw 106, screw mounting (nut) 107 and others provided between the lamp unit 100 and car body 103. One of such optical axis adjusters in pair is intended for a horizontal optical axis adjustment and the other (not illustrated) is for a vertical adjustment.
It should be noted that in the detailed-description part of this Specification and Claims, a term "front of the headlight" refers to the outside of the car body 103 from which a light beam is projected forward from the headlight while a term "back of the headlight" refers to the inner side of the car body 103 opposite to the "front of the headlight".
The adjusting screw 106 is installed as penetrated through the car body 103 and retained with a push nut or wave washer 108 which allows the adjusting screw 106 to be turned but not to be moved axially thereof. The lamp unit 100 is provided with a fixture 109 in which a screw mounting 107 is fitted non-rotatably. The adjusting screw 106 is screwed in the screw mounting 107.
The adjusting screw 106 is projected at one end thereof to the back of the headlight from the car body 103. It has a screw head 110 formed at the one end thereof.
Now, the operation for optical axis adjustment will be explained herebelow. First at the back of the headlight, an adjusting tool (not shown) is engaged into a socket in the screw head 110 of the adjusting screw 106. The screw head 110 is formed like a socket head of a bolt. As the adjusting tool is turned, the screw mounting 107 is moved as screwed along the axis of the adjusting screw 106 thus turned. Correspondingly, the lamp unit 100 is tilted horizontally about an axis connecting the pivot mechanism 104 and the vertical optical-axis adjuster (not shown).
FIG. 1 illustrates only the horizontal optical axis adjuster but not the vertical one. The vertical optical axis adjuster is generally identical in construction and action to the horizontal one.
With the prior-art optical axis adjusting device, the optical axis can only be adjusted at the back of the headlight.
Also, if the adjusting screw 106 is turned excessively in the direction in which the screw mounting 107 is moved toward the front of the headlight, the adjusting screw 106 may possibly come off the screw mounting 107.